Linear shunted transformer

ABSTRACT

There is disclosed a shunted transformer having a magnetic circuit of a primary core, a secondary core and two connecting magnetic elements forming a magnetic circuit between opposite poles of the cores, at least one primary coil surrounding the primary core, at least one secondary coil surrounding the secondary core, the primary and secondary cores positioned with their long axes parallel and their short axes non-parallel to form tapered faces, and a tapered magnetic shunt movable into and out of contact with the tapered core faces.

United States Patent Gibson Sept. 5, 1972 [54] LINEAR SHUNTED TRANSFORMER [72] Inventor: William Wallace Gibson, Concord,

Calif.

[73] Assignee: Glenn Company,

Pacheco, Calif.

[22] Filed: Jan. 7, 1972 [2]] Appl. No.: 216,135

[52] US. Cl ..336/ 133 [51] Int. Cl. ..H0lf 21/06 [58] Field of Search ..336/l30, 132, 133, 13.4

[56] References Cited FOREIGN PATENTS OR APPLICATIONS 1,030,993 3/1953 France ..336/l33 Primary ExaminerThomas J. Kozma Attorney-Harris Zimmerman 7] ABSTRACT There is disclosed a shunted transformer having a magnetic circuit of a primary core, a secondary core and two connecting magnetic elements forming a magnetic circuit between opposite poles of the cores, at least one primary coil surrounding the primary core, at least one secondary coil surrounding the secondary core, the primary and secondary cores positioned with their long axes parallel and their short axes non-parallel to form tapered faces, and a tapered magnetic shunt movable into and out of contact with the tapered core faces.

6 Claims, 4 Drawing Figures PATENTED f F|s 1,

PAIENTEHSEP 5 I912. I

saw 2 or lllIl I B'I O LINEAR SHUNTED TRANSFORMER BACKGROUND For many purposes a magnetically shunted transformer is desirable. Particularly transformers used for electric welding require varying current output that is best provided by shunting the magnetic flux between the primary and secondary coils.

In the past, magnetically shunted transformers have been made by placing a shunt in the form of a regular rectangular prism between the core within the primary coil, hereinafter the primary core, and the core within the secondary coil, hereinafter the secondary core. When positioned in contact with both the primary and secondary cores, or at least with a very small air gap separating the shunt from each core, magnetic flux is shunted from the magnetic circuit resulting in reduced current from the secondary coil. However, the nonlinear response of such a shunt makes it not entirely satisfactory. When the shunt is withdrawn a short distance, there is practically no lessening of its shunting effect because so much magnetic contact still exists between the cores and the shunt. However, when the shunt is about halfway withdrawn from between the cores, each added increment of withdrawing movement produces an increasingly larger effect. Thus when withdrawing a square or rectangular prism shunt from its position between primary and secondary cores, the first 25 percent of the distance withdrawn produces practically no effect, the next 50 percent of the distance withdrawn produces rapidly changing effect and the final 25 percent of the distance withdrawn produces such rapid rate of change of effect that close adjustment is virtually impossible.

Shunts have been designed to produce a linear effect by increasing the air gap between the shunt and the opposing cores rather than the percent of surface in contact. To provide a linearly increasing air gap requires a tapered shunt and tapered cores; and producing tapered cores is a problem. Since laminated cores are required to avoid large energy losses, tapered cores must be produced by arranging different sized and shaped laminations in a specific order which is expensive both in the fabrication of different sized laminations and in assembling them in a structure where each has a unique position with respect to all others. Additionally the tapered core faces will have a stepped configuration unless the laminations are subjected to further expenisve machining; and the stepped faces will prevent extremely close contact between the shunt and the tapered face since the resultant ledges will create a built-in air gap.

THE INVENTION This invention solves or greatly mitigates the above noted problems by providing an inexpensively constructed shunted transformer having cores made of same-sized elements conventionally stacked and fastened together. The magnetically shunted transformer of this invention includes primary and secondary cores in the form of laminated rectangular prisms which are oriented with their long axes parallel but tilted so that their faces lean toward one another. In other words, the long opposing faces of the primary and secondary cores lie in planes what would intersect if extended, or they are essentially two faces of a truncated prism. The magnetic elements that complete the magnetic circuit are oriented in the usual manner in contact with the ends of the primary and secondary cores to complete the magnetic circuit between opposite poles of the primary and secondary cores.

The shunt used in the transformer of this invention is a tapered magnetic metallic element that has faces tapered at an angle corresponding to the angle between the pyramidal faces of the opposing primary and secondary cores. The tapered shunt is also adapted to move into and out of the space between the primary and secondary cores to come into contact with both at the position of maximum penetration between them.

This invention can best be described with reference to the accompanying drawings which illustrate various structures embodying the invention. FIG. 1 is a simplified perspective view illustrating the various functional elements of the transformer of this invention. FIGS. 2, 3, and 4 are respectively an elevational view, a plan view and an end view of a transformer embodying this invention assembled and with various conventional operating features illustrated. In all views corresponding parts are referred to by the same reference numerals.

Referring to FIG. 1, there is illustrated a transformer which includes a primary coil 10 with suitable leads ll surrounding a primary core 12. The primary core and all other magnetic portions of the transformer are illustrated as laminated elements and are contemplated as being made of the usual materials for such purposes.

Opposing the primary core is a secondary core 15 surrounded by a secondary coil 13 having leads not shown. The primary core 12 and the secondary core 15 are tilted to lean toward each other in tent-like to pyramidal fashion, and the coils 10 and 13 are wrapped to assume their usual position with respect to ores l2 and 15 rather than with respect to horizontal or vertical. Connecting magnetic elements 16 and 17 complete the magnetic circuit by magnetically connecting opposite poles of cores l2 and 15.

Electric insulating sheets 18 are interposed between the contact area between cores l2 and 15 and connecting elements 16 and 17. Without such electric insulating sheets, the angular relationships between cores l2 and 15 as compared with connecting elements 16 and 17 would short out the laminations of cores l2 and 15 whereby the reduction of eddy current losses effected by the laminated construction of the magnetic elements would be lost. Insulating sheets 18 are preferably just thick enough to prevent an electrical connection between magnetic elements but not so thick as to provide a non-magnetic gap that seriously interferes with the flow of magnetic flux. The construction illustrated thus maintains the magnetic circuit substantially intact but prevents formation of an electric circuit between adjacent laminations.

Finally, shunt 20 is provided with opposing parallel faces 21 and 22 of which only face 21 is visible, and opposing tapered faces 23 and 24 of which only face 23 is visible. Shunt 20 is also provided with a driving means 25 for inserting it between cores 12 and 15 and for adjusting its position to regulate the size of the air gaps between each of cores 12 and 15 and the tapered faces 23 and 24 of the shunt. With only one coil on each of cores l2 and 15, shunt 20 will move toward contact with cores 12 and 15 either in front of or behind coil and 13 as illustrated. Preferably each of cores 12 and will be provided with two coils and shunt will contact cores 10 and 13 between the coils to provide an electrically and magnetically symmetrical structure.

FIGS. 2, 3 and 4 illustrate a transformer embodying this invention in a more conventional structure,

although all of the elements illustrated in FIG. 1 are present. In FIGS. 2, 3 and 4the primary core 10 is surrounded by two spaced primary coils 10 with a space between them being large enough to accommodate shunt 20. The secondary ore 15 is also provided with two secondary coils 13 similarly spaced. Magnetic connecting elements 16 and 17 complete the magnetic circuit through insulating sheets 18.

A frame 30 is employed as the main structural element to hold the above-described elements in the desired relationship to each other, as well as to provide a support of the means provided to drive shunt 20 into and retract it from it position between cores l2 and 15. Shunt driving means is illustrated in FIGS. 2, 3 and 4 as a bar on which the base of shunt 20 rests. Driving means 25 is engaged with two threaded elements 31 which are connected through gears 32 and chain 33 so that both of threaded elements 31 turn in the same direction at the same speed when crank 34 is operated. An element 35 in the form of a large cylinder operates in a hole in the end of frame opposite the end on which crank 34 is fixed, and cylinder is firmly fixed to the end of shunt 20. Cylinder 35 acts as a guide to assure that the insertion and withdrawal of shunt 20 are properly aligned so that approximately the same air gap exists between faces 23 and 24 of shunt 20 and cores 12 and 15.

Other conventional structural elements, such as angle irons 36 and bolts 37 are employed in their usual manner to hold cores, connecting elements, etc., in their desiredrelationship to each other.

It is evident that many equivalent structures embodying this invention may be made within its broad scope and that the accompanying drawings and foregoing description thereof are illustrative of the invention rather than limiting.

What is claimed is:

1. A linearly shunted transformer comprising a primary coil, a secondary coil, a magnetic circuit, and a tapered, movable magnetic shunt, said magnetic circuit including a primary core encircled by said primary coil, a secondary core encircled by said secondary coil with the primary and secondary cores having rectangular cross sections, having their longitudinal axes parallel and their short axes non-parallel and tapered to form tapered opposing faces of tapered truncated pyramidal form, said magnetic circuit additionally including two connecting magnetic elements each of which magnetically connect opposite poles of said primary and secondary cores to each other, and said shunt having tapered faces adapted to move into surface-contact with tapered faces of said primary and secondary cores, and to be linearly movable between said primary and secondary cores into and out of contact with said tapered faces.

2. The transformer of claim 1 wherein said primary core is encircled by two spaced primary coils, said secondary core is encircled by two spaced secondary COllS, an said movable shunt is aligned to move into and out of the magnetic circuit between each spaced pair of coils.

3. The transformer of claim 1 wherein electric insulation is disposed between said primary and secondary cores, and said connecting magnetic elements.

4. The transformer of claim 1 in which aid shunt is provided with opposed parallel aces disposed between said tapered aces.

5. The transformer of claim 1 including drive means for linearly moving said shunt towards and from said tapered core faces.

6. The transformer of claim 5 in which said driv means includes a manually engageable crank. 

1. A linearly shunted transformer comprising a primary coil, a secondary coil, a magnetic circuit, and a tapered, movable magnetic shunt, said magnetic circuit including a primary core encircled by said primary coil, a secondary core encircled by said secondary coil with the primary and secondary cores having rectangular cross sections, having their longitudinal axes parallel and their short axes non-parallel and tapered to form tapered opposing faces of tapered truncated pyramidal form, said magnetic circuit additionally including two connecting magnetic elements each of which magnetically connect opposite poles of said primary and secondary cores to each other, and said shunt having tapered faces adapted to move into surface-contact with tapered faces of said primary and secondary cores, and to be linearly movable between said primary and secondary cores into and out of contact with said tapered faces.
 2. The transformer of claim 1 wherein said primary core is encircled by two spaced primary coils, said secondary core is encircled by two spaced secondary coils, and said movable shunt is aligned to move into and out of the magnetic circuit between each spaced pair of coils.
 3. The transformer of claim 1 wherein electric insulation is disposed between said primary and secondary cores, and said connecting magnetic elements.
 4. The transformer of claim 1 in which aid shunt is provided with opposed parallel aces disposed between said tapered aces.
 5. The transformer of claim 1 including drive means for linearly moving said shunt towards and from said tapered core faces.
 6. The transformer of claim 5 in which said drive means includes a manually engageable crank. 